Carburetor



Oct' 25, 1949- J. H. sTREsEN-REUTER 2,486,223

CARBURETOR Filed Feb. 15, 1947 INVENTOR.

md Nm.

IRAS/iras ely-2e I/Zer HTTOPNE? hand wall of chamber 28.

Patented Oct. 25, 1949 cARBURE'roR John H. Stresen-Reuter, Birmingham, Mich., assignor to 'George M. Holley and Earl Holley Application February 15, 1947, Serial No. 728,801 4 Claims. (Cl. 261-39) The object of this invention is to improve the performance of the carburetor at high air ow and at high altitudes. p

Heretofore there has been a tendency. at high air flow-high altitude forthe carburetor to lean out when the ordinary altitude correction means are used. A slight increase in-richness at high air ow at extremely high altitudes vis `preferable to leaning out at high altitudes-high air ows.

I-have discovered that if I control the altitude responsive device by the pressure downstream from the smaller of the two venturis, which are lusually used, and throttle the flow through this venturi by the altitude responsive means, then the drop in pressure in the throat of the smaller of the two venturiswill approximately very closely to the correct value of Venturi suction required to maintain a constant fuel/air ratio -when the drop in the throat in the smaller .of the two venturis is balanced against the pressure drop through the fuel metering orifice.

The gure showsdiagrammatically the preferred form of my invention.

In the figure, I is the air entrance, |02 'is the temperature responsive element located in the air entrance. |04 is the casing containing-the pressure responsive element 88 located in the air entrance I0. I2 is the main venturi. |4|6 are the throttles. I8 is the fuel nozzle discharging on the engine side of the throttles |4|6. 20 is the fuel entrance into the vapor separating chamber 22 containing the float 24, iioat needle 88 and the vapor outlet |00. l

26 is the conventional fuel entrance valve. 28 is the fuel chamber ywhich vdelivers fuel past the metering needle 30. Foremergency use (idling) a valve 32 is provided. The chamber 34 communicates with the downstream side of the valve 30. Chamber 34 is located at the left hand side of the diaphragm 36, which diaphragm is the left Corresponding diaphragm 38 is located between the two air chambers 40 and 42. A small fuel chamber 44 is connected through the passage 46 and the opening 48 to the chamber 34. A small diaphragm 50 separates the fuel chamber 44 from the air chamber'42. A rod 52 connects the diaphragm 50 with the diaphragm 38. Rod 54 connects the diaphragm 88 with a small diaphragm I identical with diaphragm 50. This diaphragm 5I separates the air chamber 40 from the fuel chamber 34. Rod 66 connects the diaphragm 5| with the diaphragm 36. Rod 60 connects the diaphragm 36 with the valve 26. A spring 62 maintains the valve 26 slightly oi its seat so that the valve 32 can control the idle in spite of the fact that the air ow is so low that there is no pressure differences acting on the diaphragm 38.

64 is a temperature responsive bellows connected to the temperature responsive element I 02. Valve 66 is connected to the temperature re- "sponsive bellows 64 and moves to the right when the temperature in the air entrance I0 rises.

Bypass 68 delivers fuel under pressure from the chamber 28 to the valve 66.* Passage l0 connects the fuel flowing by the valve66 with the chamber 34. Fuel pipe 'l2 conveys the fuel flowing by the metering valve 30 to the lfuel discharge valve I8. The impact tubes 14 transmit air under pressure to the annular chamber 90surrounding the air entrance I0. This air pressure is transmitted to the chamber-42, to the left of the diaphragm 38.

. The air iiows from the annular chamber 90, down the inclined passage, through the small venturi 86, through the valve 80, down the passage |06, through the opening |08 into the point of maximum suction of the venturi I2. The streamlined obstruction 96 completes the venturi I2.

The pressure responsive element 88 in the chamber 82 is adjusted vby the adjustable screw 16 .and is responsive to the pressure at the upstream side of the valve through openings I0.

Operation increases there ls a pressurerdier'ence established on the diaphragm 38 in a well known manner. In

a similar way there is a pressure difference created on the diaphragm 36. By a well known means, namely by the valve 26, thefuel/air ratio is maintained substantially constant over a wide range of air flows. When the temperature becomes abnormally low (as it does at high altitudes) the valve 6 6 is drawn to the left andthe fuel pressure in the chamber 28 is bled through the passage 68'|0, past the valve 66 so that it takes a greater fuel ow to balance the pressure responsive to air llow. Thus the fuel/air ratio is substantially constant despite the dropin temperature at high altitudes. c l Y The temperature responsive means shown, namely |02-64--66, may be dispensed with and the ilow through the passage 68-'-10 completely stopped. In that event a slight quantity of nitrogen is admitted to the evacuated bellows 88 and ak partial correction for temperature is. obtained.

through the passage 92 is diminished because the valve 80 throttles the flow through the passage |08 as the pressure transmitted through the opening |10 to the chamber 82 falls. Therefore the pressure drop through the small venturi 86 is added to the pressure drop due to altitude.

I have discovered that by making the bellows 88 responsive to the drop downstream from the small venturi B6 I get nearer perfect compensation for load and altitude than I do if the bellows respond to the pressure in the venturi I2 or alternatively to the pressure in the air entrance I0. If the bellows respond to pressure in the air entrance I the mixture becomes rich at high altitude-high air flow. If the bellows respond to the pressure in the venturi i2 the tendency would be for the mixture ratio at high altitudes-high air flow to become slightly lean.

What I claim is:

1. Air metering means for an aircraft pressure type carburetor adapted to maintain a combustible mixture at all air ows and at all altitudes comprising an air entrance, a first venturi therein, a second venturi discharging into the throat of the first venturi, a throttle valve in the outlet of said second venturi, barometric bellows adapted to move said throttle toward the closed position at high altitudes, a chamber enclosing said barometric bellows, a passage connecting said chamber to the outlet from said second venturi on the upstream side of said throttle valve.

2. A device as set forth in claim 1 in which the chamber enclosing said barometric means is located so as to respond to the temperature of the air in the air entrance and the barometric bellows are partially filled with a gas so as to respond to temperature in the air entrance.

3. A device as set forth in claim 1 which is combined with a temperature responsive element located in the air entrance, a temperature responsive valve connected to said element, a main fuel supply passage, a restriction therein, a moving'wall responsive to the drop of fuel pressure at said restriction, a fuel valve controlling the flow of the fuel supply connected to said moving wall so that the fuel valve is moved towards its closed position by said moving wall as the fuel flow increases, a second moving wall responsive to the pressure difference between the air entrance pressure and the pressure in the throat of said second venturi also connected to said fuel valve so as to move said fuel valve towards its open position as the air flow increases, a relatively small bypass around said fuel restriction, said temperature responsive valve being located in said bypass and being adapted to be moved to its closed position as the temperature in the air entrance increases.

4. Fuel and air metering means for an aircraft pressure type carburetor adapted to maintain a combustible mixture at all air ows and at all altitudes comprising an air entrance, a rst venturi therein, a second venturi discharging into the throat of the first venturi, a throttle valve in the outlet Ifrom the second venturi, pressure responsive bellows adapted to move said throttle toward the closed position at low pressures, a chamber enclosing said bellows, a passage connecting said chamber 'to the outlet from said second venturi, a temperature responsive element located in the air entrance, a temperature responsive valve connected to said element, a main fuel supply passage, a restriction therein, a moving wall responsive to the drop of fuel pressure at said restriction, a fuel valve controlling the ow of the fuel supply connected to said moving wall so that the fuel valve is moved towards its closed position by said moving wall as the fuel flow increases, a second moving wall responsive to the pressure difference between the air entrance pressure and the'pressure in the throat of said second venturi also connected to said fuel valve so as to move said fuel valve towards its open position as the air flow increases, a relatively small bypass around said fuel restriction, said temperature responsive valve being adapted to be moved to its closed position as the temperature in the air entrance increases.

JOHN H. STRESEN-REUTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

